I have. The bags make a great substitute to actual luggage and allow you to circumvent fees. Most airlines don't make an issue of carrying them on because the measurements are just right and they're not rigid. One can stuff them in the overhead bins and still compress the sides of the bag, if necessary. The airline industry bleeds money at an unbelievable rate and has resorted to all kinds of nonsensical fees to make money. It's shameful how terrible the airlines have become in this respect.